Alkylene oxide-lactone copolymers

ABSTRACT

A block copolymer is disclosed, which comprises a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone, said copolymer being obtainable by polymerising an alkylene oxide in the presence of an organic initiator to form said first block and reacting the first block with a mixture of an alkylene oxide and a lactone. Such copolymers are found to have improved foam inhibition characteristics whilst maintaining their biodegradable properties.

[0001] This invention relates to alkylene oxide-lactone copolymers, andtheir uses.

[0002] Co- and homo-polymers of alkylene oxide are widely used asnon-ionic surfactants, foam control agents, mineral wetting agents,emulsifiers, de-emulsifiers, dispersants, and synthetic lubricants. Inparticular, polyoxyalkylene copolymers made from propylene oxide,1,2-buttlene oxide and ethylene oxide represent a major class of suchmaterials.

[0003] Alkylene oxide-lactone block copolymers are also known to beuseful for similar applications. U.S. Pat. No. 5,525,702, for example,describes a copolymer comprising a first block comprising polymerisedunits of one or more alkylene oxides and one or more lactones, and asecond block comprising polymerised units of one or more alkyleneoxides. Such compounds are prepared by polyrnerising the lactone andalkylene oxide monomers of the first block in the presence of an organicinitiator, and then capping the resulting polymer with the alkyleneoxide monomer of the second block

[0004] The presence of a lactone in the first block-of U.S. Pat. No.5,525,702 is said to introduce ester functionality into the copolymer,which in turn, enhances its overall biodegradability.

[0005] We have now found that by introducing a lactone into the secondblock of the copolymer rather than the first, the foam inhibitingproperties of the compound may be enhanced without compromising theenhanced biodegradability afforded by the presence

[0006] According to the present invention, there is provided a blockcopolymer comprising a first block comprising polymerised units of analkylene oxide and a second block comprising polymerised units of analkylene oxide and a lactone, said copolymer being obtainable by:

[0007] polymerising an alkylene oxide in the presence of an organicinitiator to form said first block, and

[0008] reacting the first block with a mixture of an alkylene oxide anda lactone.

[0009] Typically, one end of the first block is bonded directly to theorganic initiator, whilst the other end of the first block is bondeddirectly to the second block of the copolymer of the present invention.The recurrence of the alkylene oxide and lactone groups within secondblock is typically random, but may contain some degree of blockcharacter.

[0010] The copolymer of the present invention may have a molecularweight of 200 to 6000, preferably, 400 to 4000, most preferably 500 to2500. The molecular weight of the first block is typically 200 to 3000,preferably 200 to 1000 and most preferably 250 to 600; whilst themolecular weight of the second block is typically no more than 6000,preferably 500 to 4000 and most preferably 1000 to 3000.

[0011] The number of monomer units in each of the first and secondblocks may independently range from 1 to 100, preferably 5 to 50. In thesecond block, the mole ratio of alkylene oxide to lactone units mayrange up to 99:1, but is preferably 10:1 or less.

[0012] The alkylene oxide components of the copolymer include those offormula (I)

[0013] in which each R is independently hydrogen, C₁-C₆ alkyl or C₁-C₆haloalkyl. Alternatively, the two R substituents may, together with bothvicinal epoxy carbons, form a saturated or monoethylenically unsaturatedcycloaliphatic hydrocarbon ring, of preferably five or six carbon atoms.The preferred alkylene oxide monomers contain 2 to 12 carbon atoms.Examples include ethylene oxide, propylene oxide, butylene oxides,1,2-epoxydodecane, cyclopentene oxide, cyclohexene oxide and styreneoxide. Of these, butylene oxides (particularly 1,2-butylene oxide),propylene oxide and ethylene oxide are most preferred. The alkyleneoxide of the first block may be the same as the alkylene oxide of thesecond block. Preferably, however, the alkylene oxides of the first andsecond blocks are different. In a preferred embodiment, for example,ethylene oxide is employed to form the first block of the copolymer,whilst propylene oxide or 1,2-butylene oxide is employed to form thesecond block of the copolymer.

[0014] The alkylene oxide portions of both first and second blocks ofthe copolymers of the present invention may optionally comprise mixturesof alkylene oxide monomers, e.g. a mixture of ethylene and propyleneoxides.

[0015] The lactone used in the present invention may be any lactone orcombination of lactones having at least four carbon atoms in the ring,and these lactones include those of formula (II)

[0016] in which when n is at least 1 and each R¹ is independentlyhydrogen, C₁-C₄ alkyl, C₁-C₆ cycloalkyl, C₁-C₄ alkoxy or single ringaromatic hydrocarbon; with the proviso that when n is 2, at least fourR¹ in total are hydrogen.

[0017] The lactones preferred as starting materials for the second blockof the present invention include unsubstitued ε-caprolactones,ε-caprolactones substituted on the carbon atoms in the ring by one, twoor three lower (e.g. one to four carbon atoms) alkyl radicals, andunsubstituted δ-valerolactones and γ-butyrolactones. The preparation ofunsubstituted lactones is well known. The substituted c-caprolactones,and mixtures of such lactones, can readily be prepared by reacting acorresponding substituted cyclohexanone with an oxidizing agent such asperacetic acid. The cyclohexanones may be obtained from substitutedphenols or by other convenient synthetic routes. Other lactones that aresuitable as starting materials include alkoxy ε-caprolactones such asmethoxy and ethoxy ε-caprolactone, cycloalkyl, aryl and aralkylε-caprolactones such as cyclohexyl, phenyl and benzyl c-caprolactone,and lactones such as ζ-enantholactone and η-caprylactone which have morethan six carbon atoms in the ring.

[0018] The ε-caprolactones are the preferred lactones used to make thesecond block of the copolymer of the present invention. These includethose of formula (III)

[0019] in which each R² is independently either hydrogen or a C₁-C₄alkyl or C₁-C₄ alkoxy radical, with the proviso that no more than threeR² substituents are groups other than hydrogen. Unsubstitutedε-caprolactone is the preferred ε-caprolactone.

[0020] The copolymer is prepared by first polymerizing an alkylene oxideor mixture of alkylene oxides using an organic initiator. The initiatoris preferably mono-functional. Examples include alcohols, amines,mercaptans, phenols, amino alcohols and mercapto alcohols. Hydroxyl andamino terminated initiators are preferred.

[0021] Suitable monohydroxyl initiators include those represented by theformula (IV)

R³(OR⁴)_(a)OH  (IV)

[0022] in which R³ is hydrocarbyl such as alkyl, cycloalkyl, aryl,aralkyl, alkaryl, etc., preferably containing up to 18 carbon atoms; R⁴is an alkylene radical preferably containing from two to four carbonatoms; and a is an integer having a value of 0 to 18, preferably a valueof 0 to 2. Illustrative monohydroxyl initiators include the alkanols,e.g. methanol, ethanol, isopropanol, n-butanol, 2-ethylhexanol,dodecanol, tridecanol, and tetradecanol; the monoalkyl ethers of glycolsand polyglycols, e.g., 2-ethoxyethanol, 2-propoxyethanol,2-butoxyethanol, the mono ethyl ethers of diethylene glycol, oftriethylene glycol, of tripropylene glycol; the monopropyl ethers ofpolyethylene glycol, of polypropylene glycol, of polybutylene glycol;and the alkylene oxide adducts of substituted and unsubstituted phenols,e.g. the ethylene oxide and/or propylene oxide adducts of alkylphenolssuch as nonylphenol. Mixtures of organic initiators may be employed.

[0023] The initiator may alternatively be polyfunctional. Preferredpolyfunctional initiators have at least two and possibly up to 20reactive hydrogens in the form of hydroxyl groups. The polyfunctionalinitiators include compounds of the formula (V)

R⁵(YH)_(b)  (V)

[0024] where R⁵ is an aliphatic, aromatic or heterocyclic radical, b isat least 2, and each Y is —O—, —S—, —NH— or NR⁶ where R⁶ is hydrocarbyl.Preferred such initiators are diols, polyols, diamines, hydroxy aminesand thiols, such as ethylene/propylene glycol, diethylene/dipropyleneglycol, 1,2-dibutylene glycol, glycerine, trimethylol propane,pentaerythritol, ethylenediamine, ethanolamine etc. Such compounds mayalso be ethoxylated.

[0025] The polymerisation of alkylene oxide and/or alkylene oxide andlactone may be carried out in the presence of a catalyst. Any catalystthat will promote the necessary polymerization reaction may be employed.Representative catalysts include alkali metal and alkaline earthhydroxide, and Lewis acids. Preferred catalysts are the alkalihydroxides, particularly potassium hydroxide (KOH). The catalyst may beused in catalytically significant amounts which is a function of manyvariables, including the nature and quantities of reactants,temperature, mixing, and the like. Catalyst concentrations of about0.001 to about 2 weight percent are typical, with a concentration ofabout 0.01 to about 1 weight percent being preferred. It may benecessary to neutralise the catalyst prior to recovering the polymerproduct.

[0026] The copolymer of the present invention may be prepared at areaction temperature of 75 to 175° C., preferably 85 to 150° C. Thesetemperature ranges may be suitable for the formation of both the firstand second blocks of the copolymer of the present invention. Reactionpressures range from, but are not limited to, 1 to 15 bar, preferably 6to 10 bar. Preferably, anhydrous conditions are employed. The reactionmay be performed on a batch, semicontinuous or continuous basis.

[0027] The copolymers of the present invention are useful, among otherthings, as nonionic surfactants, foam control agents and lubricants.

[0028] According to a further aspect of the present invention, there isprovided a process for producing a block copolymer having a first blockcomprising polymerised units of an alkylene oxide and a second blockcomprising polymerised units of an alkylene oxide and a lactone, saidprocess comprising:

[0029] polymerising an alkylene oxide using an organic initiator to formsaid first block, and

[0030] reacting the first block with a mixture of an alkylene oxide anda lactone.

[0031] In a further embodiment of the invention, the second block itselfcomprises alternate blocks of alkylene oxide and lactone rather thanrandomly distributed units of each as in the above-described cases.Preferably the total number of blocks of alkylene oxide and lactone inthe copolymer is between 5 and 9. Preferably the copolymer has at least3 units of alkylene oxide in each block thereof, or 2 units of lactonein each block thereof. In the process associated with this embodiment,instead of being reacted with a mixture of alkylene oxide and lactone,the first block is reacted alternately with either alkylene oxide orlactone. The number of such reactions is preferably between 4 and 8 (soas to give between 5 and 9 blocks in total).

EXAMPLES

[0032] Biodegradability

Example 1

[0033] To a mixture of ethoxylated dodecanol/tetradecanol (availablecommercially as Softanol 120, a product of the Nippon shokubai company),molecular weight 711, was added potassium hydroxide as catalyst. To thismixture was added a blend of propylene oxide (4 parts molar) andcaprolactone (1 part molar) in a pressurised vessel inerted withnitrogen, reaction occurring at a temperature of 120 to 130° C., suchthat the final product had a theoretical molecular weight of 2990.Biodegradability [OECD 301b Sturm test, 28 days] 85% Cloud point [1%aqueous] 6-8° C.

Example 2

[0034] To a mixture of ethoxylated dodecanol/tetradecanol (availablecommercially as Softanol 120, a product of the Nippon shokubai company),molecular weight 711, was added potassium hydroxide as catalyst. To thismixture was added a blend of propylene oxide (5 parts molar) andcaprolactone (1 part molar) in a pressurised vessel inerted withnitrogen, reaction occurring at a temperature of 120 to 130° C., suchthat the final product had a theoretical molecular weight of 1740.Biodegradability [OECD 301b Sturm test, 28 days] 55% Cloud point [1%aqueous] 6-8° C.

Example 3

[0035] To a mixture of ethoxylated dodecanol/tetradecanol (availablecommercially as Softanol 120, a product of the Nippon shokubai company),molecular weight 683, was added potassium hydroxide as catalyst. To thismixture was added a blend of propylene oxide (2.5 parts molar) andcaprolactone (1 part molar) in a pressurised vessel inerted withnitrogen, reaction occurring at a temperature of 120 to 130° C., suchthat the final product had a theoretical molecular weight of 1176.Biodegradability [OECD 301b Sturm test, 28 days] 60% Cloud point [1%aqueous] 15° C.

Example 4 (comparative)

[0036] To a mixture of ethoxylated dodecanol/tetradecanol (availablecommercially as Softanol 120, a product of the Nippon shokubai company),molecular weight 700, was added potassium hydroxide as catalyst. To thismixture was added a blend of propylene oxide in a pressurised vesselinerted with nitrogen, reaction occurring at a temperature of 120 to130° C., such that the final product had a theoretical molecular weightof 2800. Biodegradability [OECD 301b Sturm test, 28 days] 7% Cloud point[1% aqueous] 8-15° C.

[0037] The above results show very clearly that the presence of thelactone, even though in the second block rather than the first,substantially improves biodegradability.

[0038] Antifoam Properties

Example 5

[0039] To a mixture of principally C₁₂/C₁₃ primary alcohols (availablecommercially from Condea as Lial 123), was added potassium hydroxide ascatalyst. The mixture was then ethoxylated with 12 molar equivalents ofethylene oxide in a pressurised vessel inerted with nitrogen, reactionoccurring at a temperature of 120 to 130° C. To this intermediate wasadded a blend of propylene oxide (4 parts molar) and cap at rolactone (1part molar), such that this blend made up 76% of the final composition.

[0040] The resulting copolymer had a cloud point of <8° C.

[0041] The anti-foam properties of the resulting copolymer were testedaccording to the following procedure, which is a variation of thestandard test method IP 146/73.

[0042] The apparatus for performing the foaming test comprised a 1000 mlmeasuring cylinder immersed in a water bath at the appropriatetemperature. 200 ml of sample (usually a sugar/saponin solution) wasplaced in the measuring cylinder and allowed to reach the temperature atwhich the water bath was set (usually 25° C. for FCC P12 antifoamtesting). An air pipe having a diffuser stone at its open end was placedinto the sample, and air blown through at a fixed rate for a set periodof time. After a certain measured length of time (2-5 minutes) theheight of foam in the measuring cylinder was recorded. The volume offoam created could then be compared with the volume of foam producedwhen the antifoam polymer (typically between 25 and 100 ppm) had beenadded to the sample.

[0043] The results are shown in Table 1 below.

Example 6 (comparative)

[0044] To a mixture of principally C₁₂/C₁₃ primary alcohols (availablecommercially from Condea as Lial 123), was added potassium hydroxide ascatalyst. To this mixture was added a blend of propylene oxide (4 partsmolar) and caprolactone (1 part molar) in a pressurised vessel inertedwith nitrogen, reaction occurring at a temperature of 120 to 130° C.such that this blend (propylene oxide/caprolactone) made up 76% weightof the final composition. The intermediate was then ethoxylated with 12molar equivalents of ethylene oxide (relative to the Lial 123).

[0045] The resulting copolymer has a cloud point of <8° C.

[0046] The anti-foam properties of the resulting copolymer were testedin the manner of Example 1. As can be seen from Table 1, the propertiesof Example 6, in which the lactone is present in the first block ratherthan the second, are inferior to those of Example 5. TABLE 1 foamheights (ml) at different antifoam concentrations Antifoam conc. 0 ppm50 ppm 100 ppm Example 5 650 440 150 Example 6 650 560 480

[0047] Multiple Block Copolymer

Example 7

[0048] Softanol 30, a 3 mole ethoxylate of dodecanol/tetradecanol, wasfurther ethoxylated using potassium hydroxide catalyst to give a totalof 12 moles of ethylene oxide. The product was then reacted sequentiallywith caprolactone, propylene oxide, caprolactone, propylene oxide,caprolactone and finally propylene oxide, to give a total of 7 blocks ofEO, PO and caprolactone.

[0049] The mole ratio of caprolactone to PO overall was 1:4, with eachblock of caprolactone and PO containing one-third of the total amount ofcaprolactone and PO respectively present in the copolymer. Thetheoretical molecular weight was 2990.

1. Block copolymer which comprises a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone, said copolymer being obtainable by: polymerising an alkylene oxide in the presence of an organic initiator to form said first block, and reacting the first block with a mixture of an alkylene oxide and a lactone.
 2. Copolymer according to claim 1, wherein the alkylene oxide components thereof comprise those of formula (I)

in which each R is independently hydrogen, C₁-C₆ alkyl or C₁-C₆ haloalkyl, or the two R substituents, together with both vicinal epoxy carbons, form a saturated or monoethylenically unsaturated cycloaliphatic hydrocarbon ring.
 3. Copolymer according to claim 2, wherein the alkylene oxide components thereof comprise ethylene oxide, propylene oxide, butylene oxides, 1,2-epoxydodecane, cyclopentene oxide, cyclohexene oxide or styrene oxide.
 4. Copolymer according to any preceding claim, wherein the alkylene oxides of the first and second blocks are different.
 5. Copolymer according to any preceding claim, which comprises lactones having the formula (II)

in which when n is at least 1 and each R¹ is independently hydrogen, C₁-C₄ alkyl, C₁-C₆ cycloalkyl, C₁-C₄ alkoxy or single ring aromatic hydrocarbon; with the proviso that when n is 2, at least four R¹ in total are hydrogen.
 6. Copolymer according to claim 5, wherein the lactone comprises unsubstitued ε-caprolactones, ε-caprolactones substituted on the carbon atoms in the ring by one, two or three C₁-C₄ alkyl radicals, unsubstituted δ-valerolactones, or γ-butyrolactones.
 7. Copolymer according to claim 6, wherein the lactone has the formula (III)

in which each R² is independently either hydrogen or a C₁-C₄ alkyl or C₁-C₄ alkoxy radical, with the proviso that no more than three R² substituents are groups other than hydrogen.
 8. Copolymer according to any preceding claim, wherein the molecular weight of the first block is 200 to 3000, whilst the molecular weight of the second block is no more than
 6000. 9. Copolymer according to any preceding claim, wherein the number of monomer units in each of the first and second blocks is independently between 1 and 100, and/or in the second block, the mole ratio of alkylene oxide to lactone units is 10:1 or less.
 10. Copolymer according to any preceding claim, wherein the recurrence of the alkylene oxide and lactone groups within second block is random.
 11. Copolymer according to any of claims 1 to 9, wherein the second block comprises a total of between 5 and 9 alternate blocks of alkylene oxide and lactone, each block comprising at least 3 units of alkylene oxide or 2 units of lactone.
 12. Process for producing a block copolymer having a first block comprising polymerised units of an alkylene oxide and a second block comprising polymerised units of an alkylene oxide and a lactone, said process comprising: polymerising an alkylene oxide using an organic initiator to form said first block, and reacting the first block either with a mixture of an alkylene oxide and a lactone, or alternately with either alkylene oxide or lactone. 